A Red Apple is the ending song of Gravity Rush 2, but it also appears throughout the game in more condensed form and has heavy significance to the game's plot.
Description
The song was first sung by Kat when she is accidentally mistaken for a singer on the Bismalia Fortress. Her memory returns enough to remember a few words from the song, and from this she is able to sing the entire first verse before being caught by security forces and attacked.
It then becomes extremely popular through Jirga Para Lhao and Hekseville, despite everyone only knowing the first verse.
When Kat returns to Eto, she remembers that the song was actually from a music box that her grandmother used while reading bedtime stories. She finds a key to the music box that was dropped from outside through an open window, but it's broken - the box miraculously starts working again when she is able to escape the castle, which may have been the work of Alias or one of the Creators.
The song once again appears during the battle against The Darkness, where the first verse is sung by the entire city of Hekseville to compel Kat to come to her senses and destroy The Darkness, and refuse the deal it attempted to make with her.
Lyrics
Only the first verse was officially translated to English. The rest only appears in Japanese in the game's soundtrack booklet. Credit for the translation goes to nyancatimusprime from Reddit.[1]
A red apple
Fell from the sky
Across the clouds
A gentle sun shines
On the ones we're waiting for
A red apple
A seed of hope
A beacon that shines
On me in the empty sky
Soaring once again without fear
The morning bird's song - never to be heard again
The line of burdened people goes on
They travel beyond, to the promised land
Thousands of minds surpassing their frail bodies
A dream of liberation
Don't say a word
Soaring; falling
Wherever you go, fly high
A red apple
Fell from the sky
Across the clouds
A gentle sun shines
On the ones we're waiting for
The smiles of parents - never to be seen again
A dog accompanies the people who keep on walking
They travel beyond, to the serene land
Thousands of minds surpassing their frail bodies
Disaster is far away
Don't say a word
Soaring; falling
Wherever you go, fly high
A red apple
Fell from the sky
Across the clouds
A gentle sun shines
On the ones we're waiting for
A gentle sun shines
On you
Meaning of lyrics
The song is most likely from the perspective of someone who lives in Eto. As the game says that Eto is a place where the denizens lower on the World Pillar fled to escape The Darkness as it pulled the world pillar closer. The singer is looking across the clouds atop the pillar and being reminded of "the ones they are waiting for".
The "line of burdened people" are most likely people holding their belongings and waiting to be loaded onto the Ark or some other mode of aerial transport to travel up the pillar. Since time travels slower on the bottom of the pillar than the top, people in Eto would likely face a long and agonizing wait for their loved ones, by which time they would be a lot older than the people arriving.
It's unclear what "thousands of minds surpassing their frail bodies" means, but it may be related to how the people in Eto live longer than normal.